Doctors did not release any information about the victims, other than to say that three suffered burns on half of their bodies, which they considered life-threatening injuries.
The fourth victim suffered burns on 40 percent of their body, doctors said.
The victims had been transferred from hospitals in San Mateo County, after being initially treated and stabilized, to the Bothin Burn Center at Saint Francis, which is the closest dedicated burn center, hospital officials said.
The first victim was delivered to Saint Francis between 6:30 p.m. and 7 p.m., Dr. Michael Kulick said.
Doctors will begin removing non-vital skin tissue from the patients over the next few days for skin grafts, Kulick said.
Kulick said the patients would likely remain at the burn center for at least six to eight weeks more. He said he hoped to have a better assessment of their conditions by Sunday.